Nozzle assemblies for abrasive-entrained water jet cutting are subjected to substantial wear forces by the entrained abrasive material. A typical nozzle assembly uses a mounted jewel element, having a small diameter orifice, to form the initial water jet stream from a source of high pressure water. Downstream of the jewel element, particulate abrasive material is introduced to the water jet stream. The combined water/abrasive jet stream is then directed through an elongated nozzle element wherein the abrasive material become distributed throughout the jet before leaving the assembly. If the jewel mounting or the jewel orifice is not centered exactly, the initial water stream may be off center with respect to the nozzle element. Likewise, if the nozzle element is not centered exactly in the assembly, the nozzle element may be off center with respect to the water stream. In either case, when abrasives are added to the water stream, accelerated erosion of the nozzle element will occur, resulting in much reduced life of the nozzle element. Moreover, out-of-center alignment within the assembly may also result in degrading the jet stream itself to such an extent that the cutting ability of the abrasive/water jet is markedly reduced.
A primary object of the present invention is to provide a nozzle assembly with a nozzle element centering mechanism. By the use of such a mechanism alignment of the nozzle element and the jewel element can be attained notwithstanding assembly or manufacturing errors or imperfections. A further object is to provide such a centering mechanism that can be manually adjusted while the nozzle is operating, whereby the results of the adjustment can be observed during the adjustment phase. Another object is to provide such a centering mechanism in the nozzle assembly at a location such that the nozzle element can be replaced when worn without interference with the centering mechanism.